Intensities of the neonlike iron (${\mathrm{Fe}}^{16+}$) 2${\mathit{p}}^5$3s-2${\mathit{p}}^5$3p and 2${\mathit{p}}^5$3p-2${\mathit{p}}^5$3d transitions in solar-flare spectra

We present relative spectral line intensities for 16 3s-3p and 3p-3d transitions in the neonlike ion ${\mathrm{Fe}}^{16+}$, obtained from solar-flare spectra. The spectra were obtained by a Naval Research Laboratory slitless spectrograph flown on the Skylab manned space station. The results are of relevance to x-ray-laser experiments involving collisional pumping of excited states of neonlike ions, and to the analysis of solar-flare spectra. The relative line intensities are measured to an accuracy of about 30%. The measured line intensities are compared with theoretical line intensities calculated assuming electron collisional excitation within the ${\mathrm{Fe}}^{16+}$ ion followed by deexcitation and radiative decay. The measured and theoretical intensities agree to within less than a factor of 2 for all but one line. The important J=0 lines (3 ${}_{}{}^1{}_{}{}^{}\mathrm{S}_0^{}{}_{}{}^{}$–3s ${}_{}{}^1{}_{}{}^{}\mathrm{P}_1^{}{}_{}{}^{}$,3s ${}_{}{}^3{}_{}{}^{}$ ${\mathit{P}}_1$) at 254.87 and 204.65 Å are about a factor of 1.4 weaker than predicted, which is almost within experimental error. The 3${\mathit{s}}^3$ ${\mathit{P}}_2$–3p ${}_{}{}^3{}_{}{}^{}$ ${\mathit{S}}_1$ line at 409.69 Å is 2.3 times weaker than predicted, and this is unexplained.